class_docstr: A standard class for observing VTK objects.
docstr: Initialize observer.
docstr_tok: ["Initialize","observer","."]
code: def __init__(
      self, event_type="ErrorEvent", log=True, store_history=False
  ):
      """Initialize observer."""
      self.__event_occurred = False
      self.__message = None
      self.__message_etc = None
      self.CallDataType = "string0"
      self.__observing = False
      self.event_type = event_type
      self.__log = log
  
      self.store_history = store_history
      self.event_history = []
  
imports: import collections
  import logging
  import os
  import re
  import signal
  import sys
  import threading
  import traceback
  from pyvista.core import _vtk_core
label_desc: Use image node_id 1 to create a new Observer object  with example: obj = Observer(event_type, log, store_history)